The present invention relates to cooling arrangements and more particularly to cooling arrangements in blades such as high pressure turbine blades in a gas turbine engine.
With high pressure turbine blades within gas turbine engines it will be appreciated that the relatively high temperatures to which the blades are subjected necessitate cooling in order that the materials from which such components are made can remain within the operational capabilities of those materials. Other components within a gas turbine engine which must be able to withstand such high temperatures and other operational requirements include nozzle guide vanes. Traditionally two approaches have been taken with regard to achieving necessary cooling. Firstly, impingement cooling is achieved through providing passages which extend along the length of the blade or other component with a coolant fluid under pressure, which then is projected through impingement orifices from the passage to a chamber beneath the surface to be cooled. In such circumstances, coolant fluid is projected towards that surface at high velocity, generating high heat transfer, thereby coking that part of the component. An alternative is simply provision of radial channels which are presented below the surface of the component. Each approach has its advantages and disadvantages. Impingement cooling generally gives significantly increased heat transfer compared to radial cooling even where ribs are utilised to create turbulence, but the necessity for impingement orifices greatly increases manufacturing complexity, cost and may reduce fatigue life.